Marines deployed at sea train with international security forces, provide humanitarian assistance during natural disasters such as the Japanese tsunami and serve as the United States’ 911 force during a crisis. “If war breaks out in the Korean peninsula, every available Marine is headed to Korea,” Spiese said.

Col. Scott Campbell, commanding officer of the 15th Marine Expeditionary Unit, said most of the Marines who will deploy under his command later this year will be getting their boots wet for the first time on a “float,” a Marine deployment on an amphibious assault ship. Iron Fist is a chance for these San Diego-based Marines to practice amphibious operations — a defining feature of the Corps that separates it from being a second land army.

“Whether we’re in the Pacific or the Middle East, the MEU plays the away game. We don’t even know what sport we’re going to play, whether it will be humanitarian assistance or flying airstrikes into Afghanistan,” Campbell said.

“The beauty of the MEU is you don’t have to buy the real estate. You can park the ships off the coast,” Campbell added. “The flexibility of that sea-based operation, when you don’t have to pay people to use their airstrip and you don’t have to ask their permission, it gives our leadership options.”

The U.S. Marine Corps hasn’t had to fight its way onto a beach since the Korean War, but amphibious operations are becoming increasingly attractive to nations around the world.

A landing team deployed on a ship, “is flexible in a way that a lot of our other military capabilities are not,” said John Pike, a defense analyst and director of Global Security.org. An aircraft carrier fighter wing, for example, is not much use in a humanitarian crisis or an embassy rescue, he said.

But “amphibious assault is no place for amateurs. It’s extraordinarily complicated. It’s got a lot of moving parts. You’ve got to get onto the ship and you’ve got to get off the ship and across the shore and engage with the enemy. ... That’s what the Japanese and Australians are coming to the mother church for,” he said, and why in his view, “having a Marine Corps is probably more important than ever.”